Wireless Positioning Approach Using Time-Delay of Signals with a Known Transmission Pattern

1. A method of determining a location of a mobile device comprising a plurality of antennas, the method comprising: receiving signals with known radio transmission patterns at each of the plurality of mobile device antennas from a transmitting device; correlating the signal received at each particular antenna with a corresponding signal that has a same known radio transmission pattern to determine a time the signal traveled between the transmitting device and the particular antenna; determining a location of each of the plurality of mobile device antennas based on the time the signal traveled between the transmitting device and each mobile device antenna; and determining the location of the mobile device based on the location of the plurality of antennas.

2. The method of claim 1 , wherein the mobile device receives signals from a plurality of transmitting devices comprising said transmitting device, wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require synchronizing the transmitting devices.

3. The method of claim 1 , wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require calculating a distance between the mobile device and the transmitting device.

4. The method of claim 1 , wherein determining the location of the mobile device comprises solving a function that is dependent on the time the signal traveled between the transmitting device and each of the plurality of antennas of the mobile device.

5. The method of claim 1 , wherein the known radio transmission pattern comprises a known signal preamble, wherein correlating each received signal with a corresponding signal comprises correlating the preamble of the received signal with the preamble of the corresponding signal with the same known radio transmission pattern.

6. The method of claim 1 , wherein at least one received signal comprises a plurality of pilots, the method further comprising extracting the pilots from the signal, wherein determining the time the signal traveled between the transmitting device and each antenna of the mobile device further comprises using said extracted pilots.

7. The method of claim 1 , wherein the corresponding signal that has the same known radio transmission pattern is a signal with known signatures stored at the mobile device.

8. The method of claim 1 , wherein the mobile device receives signals from a plurality of transmitting devices, wherein the mobile device and each of the transmitting devices comprise a clock, wherein the mobile device and each transmitting device comprise a set of radio frequency (RF) components, the method further comprising: synchronizing the clocks of the transmitting devices; placing the mobile device next to one of the transmitting devices; and calculating a constant delay comprising (i) an offset of the mobile device clock with respect to the clocks of the transmitting devices, (ii) a delay caused by the mobile device RF components, and (iii) a delay caused by each transmitting device RF components, wherein determining the location of the mobile device further comprises using the calculated constant delay.

9. The method of claim 1 further comprising sending an acknowledgement signal from each antenna of the mobile device to the transmitting device, wherein determining the time the signal traveled between the transmitting device and each particular antenna of the mobile device further comprises determining a round trip time that the signal traveled from the transmitting device to the particular antenna of the mobile device and the acknowledgement signal traveled from the particular antenna to the transmitting device.

10. The method of claim 1 , wherein determining the time the signal traveled between the transmitting device and each antenna of the mobile device comprises: measuring a power in the received signal; and determining a time when the power of the received signal transits from a first value to a second value, the second value corresponding to a higher power level than the first value.

11. A non-transitory machine readable medium storing a program for determining a location of a mobile device comprising a plurality of antennas, the program for execution by at least one processing unit of the mobile device, the program comprising sets of instructions for: correlating signals with known radio transmission pattern received from a transmitting device at each particular antenna in the plurality of mobile device antennas with a corresponding signal that has a same known radio transmission pattern to determine a time the signal traveled between the transmitting device and the particular antenna; determining a location of each of the plurality of mobile device antennas based on the time the signal traveled between the transmitting device and each mobile device antenna; and determining the location of the mobile device based on the location of the plurality of antennas.

12. The non-transitory machine readable medium of claim 11 , wherein the set of instructions for correlating signals with known radio transmission pattern comprises a set of instructions for correlating signals with known radio transmission patterns received from each of a plurality of transmitting devices comprising said transmitting device, wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require synchronizing the transmitting devices.

13. The non-transitory machine readable medium of claim 11 , wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require calculating a distance between the mobile device and the transmitting device.

14. The non-transitory machine readable medium of claim 11 , wherein the set of instructions for determining the location of the mobile device comprises a set of instructions for solving a function that is dependent on the time the signal traveled between the transmitting device and each of the plurality of antennas of the mobile device.

15. The non-transitory machine readable medium of claim 11 , wherein the known radio transmission pattern comprises a known signal preamble, wherein the set of instructions for correlating each received signal with a corresponding signal comprises a set of instructions for correlating the preamble of the received signal with the preamble of the corresponding signal with the same known radio transmission pattern.

16. The non-transitory machine readable medium of claim 11 , wherein at least one received signal comprises a plurality of pilots, the program further comprising a set of instructions for extracting the pilots from the signal, wherein the set of instructions for determining the time the signal traveled between the transmitting device and each antenna of the mobile device further comprises a set of instructions for using said extracted pilots.

17. The non-transitory machine readable medium of claim 11 , wherein the corresponding signal that has the same known radio transmission pattern is a signal with known signatures stored at the mobile device.

18. The non-transitory machine readable medium of claim 11 , wherein the mobile device receives signals from a plurality of transmitting devices, wherein the mobile device and each of the transmitting devices comprise a clock, wherein the clocks of the transmitting devices are synchronized, wherein the mobile device and each transmitting device comprise a set of radio frequency (RF) components, the program further comprising a set of instructions for calculating, when the mobile device is placed next to one of the transmitting devices, a constant delay comprising (i) an offset of the mobile device clock with respect to the clocks of the transmitting devices, (ii) a delay caused by the mobile device RF components, and (iii) a delay caused by each transmitting device RF components, wherein the set of instructions for determining the location of the mobile device comprises a set of instructions for using the calculated constant delay.

19. The non-transitory machine readable medium of claim 11 , the program further comprising a set of instructions for sending an acknowledgement signal from each antenna of the mobile device to the transmitting device, wherein determining the time the signal traveled between the transmitting device and each particular antenna of the mobile device further comprises determining a round trip time that the signal traveled from the transmitting device to the particular mobile device antenna and the acknowledgement signal traveled from the particular antenna of the mobile device to the transmitting device.

20. The non-transitory machine readable medium of claim 11 , wherein correlating signals with known radio transmission pattern received from a transmitting device at each particular antenna in the plurality of mobile device antennas with a corresponding signal that has a same known radio transmission pattern to determine a time the signal traveled between the transmitting device and the particular antenna comprises sets of instructions for: measuring a power in the received signal; and determining a time when the power of the received signal transits from a first value to a second value, the second value corresponding to a higher power level than the first value.

21. A system for determining a location of a mobile device, the system comprising: a mobile device comprising a plurality of antennas to receive signals; a transmitting device configured to transmit signals with known radio transmission pattern to the mobile device; the mobile device configured to: receive signals with known radio transmission pattern at each of the plurality of mobile device antennas from the transmitting device; correlate the signal received at each particular antenna with a corresponding signal that has a same known radio transmission pattern to determine a time the signal traveled between the transmitting device and the particular antenna; determine a location of each of the plurality of mobile device antennas based on the time the signal traveled between the transmitting device and each mobile device antenna; and determine the location of the mobile device based on the location of the plurality of antennas.

22. The system of claim 21 further comprising a plurality of transmitting devices comprising said transmitting device, the mobile device further configured to receive signals from the plurality of transmitting devices, wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require synchronizing the transmitting devices.

23. The system of claim 21 , wherein determining the location of each of the plurality of mobile device antennas and determining the location of the mobile device do not require calculating a distance between the mobile device and the transmitting device.

24. The system of claim 21 , wherein determining the location of the mobile device comprises solving a function that is dependent on the time the signal traveled between the transmitting device and each of the plurality of antennas of the mobile device.

25. The system of claim 21 , wherein the known radio transmission pattern comprises a known signal preamble, wherein correlating each received signal with a corresponding signal comprises correlating the preamble of the received signal with the preamble of the corresponding signal with the same known radio transmission pattern.

26. The system of claim 21 , wherein at least one received signal comprises a plurality of pilots, the mobile device further configured to extract the pilots from the signal, wherein determining the time the signal traveled between the transmitting device and each antenna of the mobile device further comprises using said extracted pilots.

27. The system of claim 21 , the mobile device further comprising memory storage, wherein the corresponding signal that has the same known radio transmission pattern is a signal with known signatures stored at the mobile device memory storage.

28. The system of claim 21 further comprising: a plurality of transmitting devices comprising said transmitting device, each transmitting device in the plurality of transmitting devices comprising (i) a clock and (ii) a set of radio frequency (RF) components, wherein the clocks of the transmitting devices are synchronized; the mobile device further comprising (i) a clock and (ii) a set of RF components; the mobile device further configured to: receive signals from each transmitting device in the plurality of transmitting devices; and calculate, when the mobile device is placed next to one of the transmitting devices, a constant delay comprising (i) an offset of the mobile device clock with respect to the clocks of the transmitting devices, (ii) a delay caused by the mobile device RF components, and (iii) a delay caused by each transmitting device RF components, wherein determining the location of the mobile device further comprises using the calculated constant delay.

29. The system of claim 21 , the mobile device further configured to send an acknowledgement signal from each antenna of the mobile device to the transmitting device, wherein determining the time the signal traveled between the transmitting device and each particular antenna of the mobile device further comprises determining a round trip time that the signal traveled from the transmitting device to the particular antenna of the mobile device and the acknowledgement signal traveled from the particular antenna to the transmitting device.

30. The system of claim 21 , wherein determining the time the signal traveled between the transmitting device and each antenna of the mobile device comprises: measuring a power in the received signal; and determining a time when the power of the received signal transits from a first value to a second value, the second value corresponding to a higher power level than the first value.